Motor controlling apparatus



Aug. 30, 1949. w. J. FIELD- KOTOR CONTROLLING APPARATUS 2 Sheets-Sheet 1 'Filed Nov. 6, 1944 T YHIN /N VE/V T05 WILL/HM J F/Elp Aug. 30, W. J. FIELD MOTOR CONTROLLING APPARATUS Filed Nov. 6, 1944 2 Sheets-Sheet 2 Patented Aug. 30, 1949 MOTOR CONTROLLING APPARATUS William J. Field, Minneapolis, Minn, assignor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Application November 6, 1944, Serial No. 562,087 -,5 7 3/ I 12 Claims. (Cl. 318-202) The present invention is concerned with motor controlling apparatus and more particularly with apparatus in which a motor is operated in accordance with the amplitude of an alternating signal voltage.

It has been proposed to operate an alternating current motor in accordance with the magnitude and phase of an alternating signal voltage through the use of a discriminator circuit which is energized in one manner or the other, depending upon the phase of the alternating current. In such prior art motor controlling apparatus, it has been customary to energize the motor with the half wave rectifier output of the discriminator stage and to employ means for causing this half wave output to simulate as nearly as possible the wave shape of an alternating voltage.

An object of the present invention is to provide a motor controlling apparatus in which a motor is energized with an alternating voltage varying in phase in accordance with the phase of an alternating signal voltage.

A further object of the present invention is to provide such an arrangement in which the electronic discharge devices of the discriminator stage are conductive during both half cycles of a complete cycle of the alternating voltage.

A still further object of the present invention is to provide such an arrangement in which the motor may he reversibl operated in accordance with the phase of the signal voltage.

A still further object of the invention is to provide an arrangement of the type such as set forth in the previous objects in which the electronic discharge devices employed are of thegas filled type.

Another object of the invention is to provide an improved type of discriminator circuit in which the electronic discharge devices of the discriminator circuit are conductive during both half cycles so that the output of the discriminator circuit is an alternating voltage.

Other objects of the invention will be apparent from a consideration of the accompanying specification, claims and drawing, of which Figure 1 is a schematic showing of one form of my improved motor controlling apparatus shown as applied to the positioning of the rudder of an aircraft, and

Figure 2 is a schematic showing of a modified form of my apparatus.

Referring to the drawing for a more detailed understanding of the invention, the motor to be controlled is indicated generally by the reference numeral III. This motor comprises a squirrel cage rotor II with which are associated a pair of field windings I2 and i3. A condenser I4 is connected through conductors l5 and Hi to the field windings l2 and I3. The function of condenser as will be explained more fully later, is to cause the current through one or the other of the two field windings l2 and 13 to lead that through the other. The squirrel cage rotor H is connected through a shaft schematically shown in the drawing and indicated by the reference numeral H to a gear train IS. The gear train, in turn, is connected through a shaft l9 to a rudder operator 20.

The motor as illustrated in the application is employed for positioning the rudder operator 20 in accordance with the signal received from a gyroscope 22.

The gyroscope 22 is adapted to position a movable contact 23 of a control potentiometer 24. The control potentiometer 24 in addition to the movable contact 23 comprises a resistance element 25 over which contact 23 is movable. The potentiometer 24 is associated with a further potentiometer 26 comprising a resistor 21 and a contact 28 slidable thereover. The two resistance elements 25 and 21 are connected together to form a Wheatstone bridge. The contact 28 is operatively connected through a shaft 29 to the rudder operator 20 and is thus positioned by shaft [9. The potentiometer 26 functions as a rebalancin'g potentiometer.

Power is supplied to the system through a transformer 35. This transformer comprises a primary winding 36 and secondary windings 31 and 38. The primary winding 36 is connected to line wires 39 and 40 leading to a suitable source of power (not shown). The secondary winding 38 is employed for supplying power to the Wheatstone bridge and is connected by conductors 42 and 43 to the opposite terminals of resistor 21 of control potentiometer 26. These two terminals constitute the input terminals of the Wheatstone bridge and contacts 23 and 28 the output terminals.

The output of the bridge is employed to control the operation of motor is through four gas filled discharge devices 44, 45, 46, and 41. These discharge devices are all similar in construction. The discharge device 44 comprises an electrically heated cathode 49, a control grid 56, a shield grid 5| and an anode 52. Associated with the cathode 49 is a cathode heater 54 which is connected to any suitable source of power (not shown) such as an additional secondary of transformer 35. Similarly, the tube 45 comprises a 3 cathode 56, a control grid 51, a shield grid 58 and an anode 59. Tube 46 comprises a cathode 80, acontrol grid 6|, a shield grid 52 and an anode 63. Tube 41 includes a cathode 86, a control grid'66, a shield grid 61 and an anode 68. In each case, the cathodes have associated with them a cathode heater element. The elements of each discharge device are enclosed within a gas filled envelope. The voltage applied to the control grids o the various tubes is obtained from the control bridge through a transformer 10. This transformer comprises a primary winding 1| and four secondary windings 12, 13, 14, and 15. The upper terminal of secondary 12 is connected to control grid 50 through a conductor 11, a biasing battery 18, a protective resistor 19 and a conductor 80. The other terminal of secondary 12 is connected through conductors 8| and 82 to the cathode 49. Similarly, the lower terminal of secondary 13 is connected through a biasing battery 94,

va protective resistor 85 and a conductor 86 to the control grid 51. The upper terminal of secondary 13 is connected through a conductor 81 to the cathode 56 of the same tube 45.

The upper terminal of secondary 14 is connected through a biasing battery 89, a protective resistor 90, and a conductor 9|- to the control grid 6| of tube 46. The lower terminal of secondary 14 is connected through conductor 92 to the cathode 60. The lower terminal of secondary 15 is connected through conductor 94, biasing battery 95, protective resistor 96 and conductor 91 to the control grid 66. The upper terminal of the'secondary 15 is connected through conductors 98 and 99 to cathode 65. Thus, each of the secondaries 12, 13, 14, and 15 is connected between the grid and cathode of one of the tubes in series with a biasing battery. In each case the polarity of the biasing battery is such as to tend to render the grid negative with respect to the cathode and is of sumcient magnitude that in the absence ofany other voltage the grid is maintained at" a potential below the value at which the tubes are conductive.

The primary H of transformer 10 is connected to contacts 23 and 28 of the bridge by means of conductors I00 and IN. It will be recalled terminals of the bridge. Operation of Figure 1 The various elements are shown in the position they assume when the aircraft is in the desired attitude. Under these conditions, no one of the tubes 44 to 41 is conductive since in each case, the grid is biased negatively sufliciently to render the tube in question non-conductive. .Consequently, no current is supplied to the motor field windings I2 and I3 and the motor is inoperative. Now let it be assumed that the aircraft departs from the desired course so that the gyroscope 22 is effective to move the contact 23 to the right. The effect of this will be to cause contact 23 to be at a voltage different from that of contact 28 so that an unbalance voltage exists across the terminals of the bridge. This unbalance voltage will in turn be applied to primary winding H of transformer 10. This in turn will cause a voltage to appear across the terminals of each of the secondaries 12 to 15. The secondary windings 12 to 15 are so wound that during the half cycle in which the upper terminal of secondary 31 is positive with respect to the lower terminal, the upper terminals of secondaries 12 and 13 will be negative with respect to the lower terminals, while the upper terminals of secondaries 14 and 15 will be positive with respect to the lower terminals.

Considering the conditions during the half cycle in which the polarities mentioned in the last paragraph exist, the anode 68 of tube 41 is positive with respect to the cathode. However, the grid 66' during this half cycle is connected to what is the negative end of secondary 15. Consequently, both the voltage of secondary 15 and that of biasing battery 95 are tending to drivegrid 66 negative with respect to the cathode so that the tube 41 is effectively non-conductive. In the case of tube 46, the anode 63 is negative withrespect to the cathode so that this tube is likewise non-conductive. In the case of tube 44, the anode is negative with respect to the cathode so that the tube is non-conductive.

Let us now consider the polarities in connection with tube 45. It is to be noted that the anode 45 is connected to the end of the transformer secondary 31 which is positive during this half cycle with respect to center tap III. Moreover, the control grid 51 is connected to the lower end of secondary 13 which during this half cycle is positive with respect to the cathode. The positive voltage impressed upon grid 51 by secondary 13 thus tends to overcome the effect of biasing battery 84 so as to render tube 45 conductive. As a result, a circuit is established to motor field winding I2 as follows: from the upper terminal of secondary 31 through conductors I05 and I06, anode 59, cathode 56, conductors I01 and I08, field winding I2 and conductor IIO to the center tap III of secondary 31. At the same time, current flows to field winding I3 as follows: from the upper terminal of secondary 31, through conductors I05 and I06, anode 59, cathode 56, conductors I01, I08 and I5, condenser I4, conductor I6, field winding I3 and conductor III] to the center tap of secondary 31.

Now let the conditions in the next half cycle be considered. Since the Wheatstone bridge is connected to the same source of power as the tubes 44 to 41, it will be obvious that the polarities will be reversed throughout. Thus, in the case of tube 41, the anode 68 will be negative with respect to the cathode so that this tube will be non-conductive. While the anode 63 will now be positive with respect to cathode 60, the

control grid 6| will also have its polarity reversed so as to be negative with. respect to cathode 60.

Hence, tube 46 will be non-conductive. In the case of tube 45, the anode 59 will now be negative with respect to the cathode so that this tube will be non-conductive. As for tube 44, the anode 52 will be positive with respect to the cathode 49 and the grid 50 will now be positive with respect to cathode 49. Hence, tube 44 will be conductive during this half cycle with the result that current will flow through winding I2 as follows: from the center tap I I I of secondary 31 through conductor IIO, motor field winding I2, conductor I08, anode 52, cathode 49, and conductors 82 and I05 to the upper terminal of secondary 31. At the same time, a circuit will be established to field winding I3 as follows: from the center tap III of secondary 31 through conductor H0, field winding I3, conductor I6, condenser I4, conductors I5 and I08, anode 52, cathode 49 and conductors 92 and I05 back to the upper terminal of secondary 31.

It is to be noted from the above that tube 45 is conductive during one half cycle and tube 44 durin the other half cycle. This is due to the mam ings l2 and I3 and'during the other half cycle in the opposite direction. Thus, there is a flow of alternating current through windings I2 and II. The alternating current flow through winding I3 is through condenser l4 so that the current through this winding leads that through winding l2. Thus, the motor rotates in a'predetermined 7 direction to cause operation of the rudder in a predetermined direction. The operation of this rudder is in such a direction as to tend to restore the plane to the course which the gyroscope 2 2 is trying to maintain. Furthermore, the operation of the motor in this direction moves contact 26' to the right with respect to resistor 21. The movement of the motor will continue until the position of contact 28 again corresponds to that of contact 23, at which time the bridge will again be rebalanced so as to eliminate the unbalance voltage. This will in turn cause the disappearance of an alternating voltage across the terminals of the secondaries 12 to 15 with the result that tubes 44 to 41 all become non-conductive.

.- Thus, there will be a movement of the rudder in a direction such as to correct for the deviation of the craft from the desired course in an amount corresponding to the extent of such deviation.

The deflection of the rudder as a result of the foregoing action will cause the craft to gradually return to the desired course with the result that slider 23 is moved back to its original position. This causes slider 23 to be in a position to the left of slider 28 so as to result in an unbalance voltage appearing across the terminals of primary winding II. This unbalance voltage furthermore will be 180 out of phase with respect to the unbalance voltage previously considered. Thus during the half cycle in which the upper terminal of secondary 31 is positive with respect to the lower terminal, the polarities of the voltages appearing across secondary windings 12 to 15 will be opposite to that indicated by the legends on the drawings.

Assuming the conditions just described, the relative polarities of the various elements of the tubes 44 to 41 will now be considered. In the case of tube 44, the cathode 49 will be positive with respect to the anode so that this tube will not be conductive. In the case of tube 45, while the anode is positive with respect to the cathode, the effect of the voltage acros secondary 13 will be to cause grid 51 to be more negative with respect to cathode 56 so that this tube will not be conductive. In the case of tube 46, the anode 63 will be negative with respect to the cathode so that this tube will likewise not be conductive. tube 41, the anode 68 will be positive with respect to the cathode and the eiIect of the voltage across secondary I4 is to tend to cause grid 66 to be positive with respect to cathode 66. The-effect of the voltage across secondary 15 will overcome the biasing effect of the battery 95 so that tube 41 will be conductive and current will flow through windin l3 as follows: from the center tap Ill through conductor H8, field winding (3, conductor H5, anode 68, cathode 65 and conductors 39 and H6 to the lower terminal of secondary 31. At the same time, a circuit will be established through field winding l2 as follows: from thecenter tap Ill throughconductor 0, held wind- In the case oftion opposite to that previously considered toing i2, conductor l6, condenser l4, conductors l8 and '6, anode 68, cathode 65, and conductors 88 and 6 to the lower terminal of secondary 31.

Now let the conditions during the next half cycle be considered. Under these conditions, the lower terminal of secondary 31 will be positive with respect to the upper terminal and the polarities of the voltages across secondaries I2 to 16 will be the same as those indicated by the legends. Under these conditions, tube 44 will be non-conductive because the grid 58 will be negative with respect to the cathode. Tube will be non-conductive because of the fact that the anode will be negative with respect to the cathode 66. Tube 41 will be non-conductive because of anode 68 being negative with respect to cathode 65. Tube 46, however, will be conductive since during this half cycle the anode 63 is positive with respect to the cathode and the voltage of grid 6| will likewise be positive with respect to the cathode 68. As a result, a circuit will be established to field winding l3 as follows: from the lower terminal of the secondary 31 through conductors H6 and ill, anode 63, cathode 68, conductors H8 and '5, motor field winding I3 and conductor Hll'to the center tap III. A circuit will also be established to field winding H as follows: from the lower terminal of secondary 31 through conductors H6 and i ll, anode 63, cathode 60, conductors H8, H5, and I6, condenser l4, conductor l5, field winding l2 and conductor H8 to the center tap ill of secondary 31.

It will be observed from the above description that with the bridge unbalanced in the direction described, tubes 46 and 41 are conductive during alternate half cycles, With these tubes conductive, moreover, current flows directly through field winding l3 while flowing through field winding 12 through condenser l4. As a result an alternating current flows in both windings I2 and l3, the current through winding i2 leading that through winding i3. It will be recalled that during the previous condition of unbalance the current through winding 13 leads that through winding Thus the motor in will rotate in the direcmove the rudder back to its normal position. The slider 28 will likewise be moved back to the left, and this movement of the rudder will be continued until the positions of sliders 23 and it again correspond, at which time the rudder will be in substantially its original or neutral position. The ship will now be back on the desired course and the rudder in its normal position. The movement of contact 28 back to a position corresponding to that of contact 23 will eliminate 'the unbalance voltage appearing across the Y bridge, and hence eliminate any alternating volt- Species of Figure 2 The arrangement of Figure 2 difiers primarily from that of Figure 1 in the fact that it is possible to employ a single secondary winding of half the size of secondary winding 31 and without a center tap. This is accomplished by using the secondary winding to supply voltage to the anodes and cathodes of all four tubes. Another difference between the circuit of Figure 2 and that of Figure 1 5 is that vacuum tubes are employed instead of the gas filled tubes of Figure 1. By reason of the use of vacuum tubes with their less critical sensitivity, it is possible to employ a self-biasing arrangement for the grids and thus eliminate the need for biasing batteries 18, 3d, 89 and 95 of Figure 1.

In order to facilitate an understanding of the arrangement of Figure 2, identical reference numerals have been applied to those elements which correspond identically to elements of Figure 1. Furthermore, reference numerals one hundred higher have been applied to those elements which, while not identical to any elements in Figure l, accomplish generally similar functions.

The arrangement of the motor field windings and the condenser I4 is identical to that of Figure 1 so that no description thereof is deemed necessary. In order to avoid unnecessary duplication of description, the gear train, the rudder,

the gyroscope and the bridge have been omitted in Figure 2. It is to be understood, however, that motor I0 can be employed to operate such a rudder operator or any other similar device in the same manner as'in Figure 1. While the primary II of transformer 10 is not shown as connected to any signal voltage, it is to be understood that this can be connected to a Wheatstone bridge such as shown in Figure 1 or to any other suitable source of alternating signal voltage which is reversible in phase. The tubes in this species are designated by the reference numerals I44 to I41 and are preferably vacuum tubes. A typical tube which is suitable for this purpose is the type 2A3. Tube I44 comprises a cathode I49, 9. control grid I50, and an anode I52. Associated with the cathode I49 is a cathode heater I54 connected to any suitable energizing source (not shown). Tube I115 similarly comprises a cathode I53, a control grid I51 and an anode I59. The tube I46 has a cathode I50, a grid IBI and an anode I53.

The tube I41 comprises a cathode I65, 9, grid I35 and an anode I58. In each case, the cathode is provided with a cathode heater as in the case of tube I44.

Associated with the cathode I49 is a cathode biasing resistor 20I and a by-pass condenser 200.

Similarly, in connection with tube I45 is a cathode biasing resistor 202 and a by-pass condenser 203. Associated with tubes I46 and I41,

respectively, are cathode biasing resistors 204 55 and 206 which are by-passed by condensers 205 and 201 respectively.

The transformer I35 comprises a primary winding I36 which may be connected to any suitable source of power and a secondary wind- The lower terminal of secondary 12 is connected through conductor I11 to the grid I50. The upper terminal of secondary '13 is connected through conductor I81 to the control grid I51. The lower terminal of secondary 13 is connected through conductor I03 and biasing resistor 202 76 to the cathode 153. ,The upper terminal of sector 098 and cathode biasing resistor 205 to the cathode I65. Thus, the voltages appearing across secondaries 1'2, 13, 1d and 15 upon the occurrence of a signal voltage are impressed between the grids and cathodes of tubes to I41, respectively. In each case, the connections include the cathode biasing resistor associated with the cathode of the tube in question. This cathode biasing resistor functions in the usual manner to introduce a biasing voltage into the grid circuit by reason of the voltage drop occurring thereacross as a result of the anode current flowing through the tube. Thus, in the absence of any signal voltage, the current flowing through any tube circuit is very small due to the biasing effect of the biasing resistors.

Operation of Figure 2 Let it first be assumed that the phase of the signal voltage is such that during the half cycle in which the left-hand terminal of secondary I31 is positive with respect to the right-hand terminal, the polarities of the voltages across secondaries 12 to 15 correspond to the legends appearing on the drawings. Under these conditions, tube I41 is not conductive since the anode I08 is negative with respect to the cathode I65. Tube I46 is not conductive since the efiect of the voltage across secondary 14 is to render the grid I5I further negative with respect to the cathode I60. Similarly. tube I45 is non-conductive since the anode I59 is negative with respect to the cathode. Tube I44 is conductive, however, since the anode I52 is positive with respect to cathode I40 and the efiect of the voltage across secondary 12 is to raise the potential of grid I50 with respect to cathode I 49. As a result, current flows to field winding I2 as follows: from the left-hand terminal of secondary I31 through conductor 2I0, motor field winding I2, conductors 2H and 2I2, anode I52, cathode I49, biasing resistor 20I and conductors 2I4, 2I5 and 2I6 back to the righthand terminal of secondary I31. At the same time, a circuit is also established to motor field winding I3 as follows: from the left-hand terminal of secondary I31 through conductor 2 I0, field winding I3, conductor I6, condenser I4, conductors I5, 2 and 2I2, anode I52, cathode I49, resistor 20I and conductors 2I4, 2I5 and 2I6 to the right-hand terminal of secondary I31.

During the next half cycle, all of the polarities are reversed. Under these conditions, tube I41 is non-conductive since the grid I65 is now negative with respect to cathode I65. Similarly, tube I40 is non-conductive since the anode I63 is negative with respect to cathode I60 and tube I44 is non-conductive since the anode I52 is now negative with respect to the cathode. Tube I45 cathode I55, cathode resistor 202, conductor 2| I,

Means field winding I2. and conductor III to the lefthandterminal of secondary I31. At the same time, a circuit is established to fleldwinding I3 as follows: from'the right-hand terminal of secondary I31 through conductors 2I5, 2I6and 2I3, anode I59, cathode I55, biasing resistor 202, conductors 2H and I5, condenser I4, conductor I0, field winding I3, and conductor 2I0, to the lefthand terminal of secondary I31.

It will be seen from the above that with a signal voltage or the phase being considered, tubes I44 and I45 are conductive during all half cycles to supply alternating current directly to field winding I2 and through the condenser I4 to field winding I3. The current through field winding I3 thus leads that through. field windin I2 and the motor rotates in one direction.

When the phase of the signal voltage is reversed, the polarities of the voltages across secondaries 12 to will likewise be reversed. As a result, during the half cycle in which the voltage of secondary I31 is that indicated by the legends, the grid I50 will be negative with respect to the cathode I49 so that tube I44 will be non-conductive. During the same half cycle, the. anode I59 is negative with respect to the cathode I55. In other words, the voltages impressed upon the grids I50 and I51 are now out of phase with the anode voltages impressed on the two tubes I44 and I45. Under these conditions, the anode I68 will be negative with respect to the cathode I55 so that tube I41 will not be conductive. Tube I46 will, however, be conductive since the anode will be positive with respect to the cathode and the eflfect of the voltage across secondary 14 tends to raise the potential of the grid with respect to the cathode. As a result, a circuit will be established to field winding I3 as follows: from the left-hand terminal of secondary I 31 through conductor 2I0, field winding I3, conductors 2I0 and 2I9, anode I63, cathode I60, biasing resistor 204,and conductors I93, 220 and 2I5 to the other terminal of secondary I31. At the same time, an energizing circuit will be established to field winding I2 as follows: from the left-hand terminal of secondary I31 through conductor 2I0, field winding I2, conductor I5, condenser I4, conductors I6, H8 and 2I9, anode I63, cathode I60, biasing resistor 204, and conductors I93, 220 and 2I6 to the right-hand terminal of secondary I 31.

During the next half cycle, the polarities of the voltages across secondaries 12 to 15 will be the same as indicated in the drawing, while the voltage across the secondary I31 will be opposite to that indicated by the legends. As a result, tubes I44 and I45 will be non-conductive by reason of the anodes being negative with respect to the cathodes. Tube I45 will be non-conductive because the voltage applied by secondary 13 will tend to drive grid I51 negative with respect to cathode I56. However, the tube I41 will be conductive since the anode is now positive with respect to the cathode and the voltage applied by secondary 15 tends to raise the potential of grid I55 with respect to cathode I65. As a result of tube I41 being conductive, a circuit will be established'to field winding I3 as follows: from the right-hand terminal of secondary I31 through conductors 2I6,220, I93 and 222, anode I68, cathode I55, biasing resistor 205, conductors 223 and 2", field winding I 3 and conductor 2I0 to the left-hand terminal of secondary I31. At the same time, a circuit will be established'to field winding I2 as follows: from the right-hand terminal of secondary I31 through conductors 2I6, 225, I93

.10 I and 222, anode I 65. cathode I65, cathode resistor 205, conductors 223, 2I3 and I6, condenser I4, conductor I5, field winding I2 and conductor 2I0 to the left-hand terminal of secondary I31.

Thus again, both windings I2 and I3 are energized during opposite half cycles in opposite directions as a result of the alternative conductivity of tubes I45 and I41. In this case, field winding I3 is energized directly whereas field winding I2 is energized through condenser I4 so that the current through the latter leads that through the former, thus causing operation oi motor I0 in the opposite direction.

It is to be noted that with the species of Figure 2, as with the species of Figure 1, motor I0 is supplied with a full alternating current as distinguished from a half-wave rectified current such as is the common practice in connection with discriminator circuits. Furthermore, this is accomplished in the arrangement of Figure 2 with the use of a single secondary winding with no center tap, this secondary winding being connected in the anode circuit of all four tubes.

Conclusion It will be seen that I have provided a new and improved motor controllin apparatus by which a reversible motor can be operated in one direction or another through the operation of a dis-, criminator circuit,,and in which the voltage supplied to the motor is at all times an alternating voltage with no appreciable direct current component.

While I have shown certain specific forms of my invention for purpose of illustration, it is to be understood that the scope of my invention is to be limited solely by the scop of the appended claims.

I claim as my invention:

1. In a motor control circuit, an alternating current power source, a motor, a pair of electron tubes, each having an anode, a cathode, and a control element, one terminal of said source being connected to the cathode of the first tube and to the anode of the second tube, and the anode of the first tube and the cathode of the second tube being connected to one terminal of said motor, the other terminal of said motor being connected to the other terminal of said source, and means arranged to supply a variable potential to the control elements of each of said tubes, of the same frequency as said source and of opposite phase on the respective tubes.

2. In control apparatus for supplying alternating current to a load means in one manner or another, a source of alternating signal voltage, reversible in phase in accordance with the condition of a main controller, a source of alternating power, and means for supplying alternating current from said last named source to said load means in the one manner or the other depending upon the phase of said signal voltage, said means comprising two pairs of electronic discharge devices each having an anode, a cathode, and a control element, both pairs of devices being connected between said load means and said source of power, the anodes and cathodes of the discharge devices of each pair being reversibly pending upon the phase of said signal voltage, said last named means comprising a transformer having a primary winding and four secondary windings, said primary winding being connected to saidsource of signal voltage and said secondary windings each being connected between the cathode and control element of a difierent device.

3. In motor control apparatus, a reversible alternating current motor to be controlled and having two paths therethrough, said motor being operative in one direction or the other dependent upon which of said paths is energized, a source of alternating signal voltage reversible in phase in accordance with the condition of a main controller, a source of alternating power and means for selectively supplying power from said source to one or the other of said motor paths, said means including two pairs of electronic discharge devices each having an anode, a cathode, and a control element, each pair of devices being connected in series with one of said motor paths, the anodes and cathodes of the discharge devices of each pair being reversibly connected together so as to be conductive during alternate half cycles, and means for applying voltages to the control elements of said discharge devices related tov the signal voltage in such a manner that one or the other of said pairs of discharge devices is energized depending upon the phase of said signal voltage.

4. In motor control apparatus, a reversible alternating current motor to be controlled and having two paths therethrough, said motor being operative in one direction or the other dependent upon which of said paths is energized, a source of alternating signal voltage reversible in phase in accordance with the condition of a main controller, a source of alternating power and means for selectively supplying power from said source to one or the other of said motor paths, said means including two pairs of electronic discharge devices each having an anode, a cathode, and a control element, each pair of devices being connected in series with one of said motor paths, the anodes and cathodes of the discharge devices of each pair being reversibly connected together so as to be conductive during alternate half cycles, and means for applying voltages to the control elements of said discharge devices, the voltages applied to the control elements of the devices of either pair being reverse in phase with respect to each other and with respect to those applied to the control elements of the devices of the other pair so that the devices of one air or the other are energized during alternate half cycles, the pair that is energized depending upon the phase of said signal voltage.

5. In motor control apparatus, a. reversible alternating current motor to be controlled and having two paths therethrough, said motor being operative in one direction or the other dependent upon which of said paths is energized, a source of alternating signal voltage reversible in phase in accordance. with the condition of a main controller, a source of alternating power connected in series with both of said motor paths and means for selectively controlling the connections between said source and said two motor paths, said means including two pairs of electronic discharge devices each having an anode,

acathcde, and a control element, eachpair of devices being connected in series with 'one of said motor paths, the anodes and cathodes of the'discharge devices of each pair being reversibly connected together so as to be conductive during alternate half cycles, and means for applying voltages to the control elements oi said tubes related to the signal voltage in such a man- 5 ner that one or the other of said pairs of tubes is energized depending upon the phase of said signal voltage.

6. In motor control apparatus, a reversible alternating current motor to be controlled and having two paths therethrough, said motor being operative in one direction or the other dependent upon which of said paths is energized, a source or alternating signal voltage reversible in phase in accordance with the condition of a main controller, a source of alternating power having two portions connected in phase opposition and each connected in series with one of said paths, and means for selectively controlling the connections between said two portions and said two motor paths, said means including two pairs of electronic discharge devices each having an anode, a cathode, and a control element, each pair of devices being connected in series with one of said motor paths, the anodes and cathodes of the discharge devices of each pair being reversibly connected together so as to be conductive during alternate half cycles, and means for applying voltages to the control elements of said tubes'related to the signal voltage in such a manner that one or the other of saidv pairs of tubes is energized depending upon the phase of said signal voltage.

'I. In control apparatus for supplying alternat ing current to a load means in either of two manners, a source of alternating signal voltage reversible in phase in accordance with the condition of a main controller, a source of altemating power, and means for supplying alternating current from said last named source to saidload means selectively in one or the other of said two manners depending upon the phase of said signal voltage, said means comprising two pairs of-electronic discharge devices each having an anode, a cathode, and a control element, both pairs of devices being connected between said load means and said source of power, the anodes of the discharge devices of each pair being oppositely connected to said source soas to be conductive during alternate half cycles and oppositely connected 50 to said load means so that th current'through said load means reverses during alternate halt cycles, and means for applying voltages to the control elements of said discharge devices related to the signal voltage in such a manner that the devices of one or the other of said pairs of devices are energized during alternate half cycles,

the pair which is energized depending upon the phase of said signal voltage.

8. For control of a motor having three terminals, and which runs in one direction when curand second electron tube, each having an anode,

a cathode, and a control element, a connection between said source, the cathode of said first tube and the anode of the second tube, a connection between the first terminal of the motor, the anode of said first tube and the cathode of the second tube, a third and fourth electron tube, each hav-v said third'tube and the anode of the fourth tube, a connection between the third terminal of the motor, the anode of the third tube and the oathode of the fourth tube, means arranged to supply a variable control voltage between the control element and cathode of each of the first and second tubes, of the same frequency as said source and of opposite phase on the respective tubes, and means arranged to supply a variable control voltage between the control element and cathode of each of the third and fourth tubes, of the same frequency as said source and of opposite phase on the respective tubes.

9. For control of a motor having a pair of windings relatively displaced in space phase, having a common terminal, and each having a free terminal, a system including a center-tapped alternating current power supply, a connection between the center tap of said power supply and the common terminal of said motor windings, a connection from one terminal of the power supply to the free terminal of one motor winding, an electron tube having anode and cathode elements interposed in series with the last mentioned connection, means rendering said electron tube conductive upon the application to said means of an alternating control voltage exceeding a predetermined magnitude and having a given phase polarity with respect to that of the power supply, a connection from the other terminal of the power supply to' the free terminal of the other motor winding, a second electron tube, having anode and cathode elements interposed in series with the last mentioned connection, means rendering said electron tube conductive upon the application to said means of an alternating control voltage exceeding a predetermined magnitude and having-a phase polarity with respect to that of the power supply which is the opposite of that for the first mentioned control voltage, and a phase shifting device connected between the free terminals of the motor windings.

10. In control apparatus for supplying alternating current to a load means in one manner or another, a source of alternating signal voltage reversible in phase in accordance with the condition of a main controller, a source of alternating power, and means for supplying alternating current with substantially no unidirectional component from said last named source to said load means in the one manner or the other depending upon the phase of the signal voltage, said means comprising two pairs of electronic discharge devices each havingan anode, a cathode, and a control element, each pair of devices being so connected between said load means andsaid source of power in series with said source of power that when the devices of the pair are conductive current flows through said load means in opposite directions during alternate half cycles. and means for applying alternating voltages to the control elements of said discharge devices related to the signal voltage in such a manner that the devices or one or the other of said pairs of devices are energized during alternate half cycles, the pair which is energized depending upon the phaseof said signal voltage with respect to said source of power.

11. In control apparatus for supplying alternating current to either one or the other of two portions of a. load means, a source of alternating signal voltage reversible in phase in accordance with the condition of a main controller, a source of alternating power, and means for supplying alternating current with no appreciable unidirectional component from said last named source to one or the other of said two portions of said load means depending upon the phase of the signal voltage, said means comprising two pairs of electronic discharge devices each having an anode, a cathode, and a control element, each pair of devices being so connected between said source of power in series with said source of power and one of said two portions of said load means that when the devices of the pair are conductive current flows through the associated portion of the load means in opposite directions during alternate half cycles, and means for applying alternating voltages to the control elements of said discharge devices related to the signal voltage in such a manner that the devices of one or the other of said pairs of devices are energized during alternate half cycles, the pair which is energized depending upon the phase of said signal voltage with respect to said source of power.

12. In a motor control circuit, an alternating current power source, a motor, a pair of gas filled tubes, each having an anode, a cathode, and a control element, one terminal of said source being connected to the cathode of the first tube and to the anode of the second tube, the anode of the first tube and the cathode of the second tube being connected to one terminal of said motor, the other terminal of said motor being connected to the other terminal of said source, and means arranged to supply a variable potential to the control elements of each of said tubes, or the same frequency as said source, and of opposite phase on the respective tubes.

WILLIAM J. FIELD.

REFERENCES CITED The following references are of record in the file of this patent:

Conklin July 1, 1947 

